Releasing the former Stadia file transfer tools

The tools allow efficient and fast synchronization of large directory
trees from a Windows workstation to a Linux target machine.

cdc_rsync* support efficient copy of files by using content-defined
chunking (CDC) to identify chunks within files that can be reused.

asset_stream_manager + cdc_fuse_fs support efficient streaming of a
local directory to a remote virtual file system based on FUSE. It also
employs CDC to identify and reuse unchanged data chunks.

manifest/content_id.cc

@@ -0,0 +1,99 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "manifest/content_id.h"
+
+#include "blake3.h"
+
+namespace cdc_ft {
+namespace {
+
+// Converts |n| in the range 0..15 to its lower-case hex representation.
+// Returns -1 if |n| is not in the range 0..15.
+char IntToHex(uint8_t n) {
+  if (n <= 9) return '0' + n;
+  if (n <= 15) return 'a' + n - 10;
+  return -1;
+}
+
+// Converts the lower-case hex character |c| to its integer representation.
+// Returns -1 if |c| is not a valid lower-case hex character.
+int HexToInt(char c) {
+  if (c >= '0' && c <= '9') return c - '0';
+  if (c >= 'a' && c <= 'f') return c - 'a' + 10;
+  return -1;
+}
+}  // namespace
+
+// static
+ContentIdProto ContentId::FromDataString(const std::string& data) {
+  return FromArray(data.c_str(), data.size());
+}
+
+// static
+ContentIdProto ContentId::FromDataString(absl::string_view data) {
+  return FromArray(data.data(), data.size());
+}
+
+// static
+ContentIdProto ContentId::FromArray(const void* data, size_t len) {
+  blake3_hasher state;
+  uint8_t out[kHashSize];
+  blake3_hasher_init(&state);
+  blake3_hasher_update(&state, data, len);
+  blake3_hasher_finalize(&state, out, kHashSize);
+  ContentIdProto content_id;
+  content_id.set_blake3_sum_160(out, kHashSize);
+  return content_id;
+}
+
+// static
+std::string ContentId::ToHexString(const ContentIdProto& content_id) {
+  absl::string_view blake3_sum(content_id.blake3_sum_160());
+  std::string ret;
+  ret.reserve(blake3_sum.size() << 1);
+  for (size_t i = 0; i < blake3_sum.size(); ++i) {
+    ret.push_back(IntToHex(static_cast<uint8_t>(blake3_sum[i]) >> 4));
+    ret.push_back(IntToHex(static_cast<uint8_t>(blake3_sum[i]) & 0xf));
+  }
+  return ret;
+}
+
+// static
+bool ContentId::FromHexString(const std::string& str,
+                              ContentIdProto* content_id) {
+  if (str.size() != kHashSize * 2) return false;
+
+  std::string* hash = content_id->mutable_blake3_sum_160();
+  hash->clear();
+  hash->reserve(kHashSize);
+  for (int n = 0; n < str.size(); n += 2) {
+    int high = HexToInt(str[n]);
+    int low = HexToInt(str[n + 1]);
+    if (high == -1 || low == -1) {
+      hash->clear();
+      return false;
+    }
+    hash->push_back((high << 4) + low);
+  }
+
+  return true;
+}
+
+// static
+uint8_t ContentId::GetByte(const ContentIdProto& content_id, size_t pos) {
+  if (pos >= content_id.blake3_sum_160().size()) return 0;
+  return content_id.blake3_sum_160()[pos];
+}
+}  // namespace cdc_ft